<div class="refentry" title="glViewport"><a id="glViewport"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glViewport — set the viewport</p></div><div class="refsynopsisdiv" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glViewport</b>(</code></td><td>GLint <var class="pdparam">x</var>, </td></tr><tr><td> </td><td>GLint <var class="pdparam">y</var>, </td></tr><tr><td> </td><td>GLsizei <var class="pdparam">width</var>, </td></tr><tr><td> </td><td>GLsizei <var class="pdparam">height</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term">
		    <em class="parameter"><code>x</code></em>,
		    <em class="parameter"><code>y</code></em>
		</span></dt><dd><p>Specify the lower left corner of the viewport
		    rectangle, in pixels. The initial value is (0, 0).</p></dd><dt><span class="term">
		    <em class="parameter"><code>width</code></em>,
		    <em class="parameter"><code>height</code></em>
		</span></dt><dd><p>Specify the width and height of the viewport. When
		    a GL context is first attached to a surface (e.g. window),
		    <em class="parameter"><code>width</code></em>
		    and
		    <em class="parameter"><code>height</code></em>
		    are set to the dimensions of that surface.</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="description"></a><h2>Description</h2><p>
	<code class="function">glViewport</code>

	specifies the affine transformation of
	<em class="replaceable"><code>x</code></em> and
	<em class="replaceable"><code>y</code></em>
	from normalized device coordinates to window coordinates. Let
	<math overflow="scroll"><mfenced>
	    <msub><mi>x</mi><mi>nd</mi></msub>
	    <msub><mi>y</mi><mi>nd</mi></msub>
	</mfenced></math>
	be normalized device coordinates. Then the window coordinates
	<math overflow="scroll"><mfenced>
	    <msub><mi>x</mi><mi>w</mi></msub>
	    <msub><mi>y</mi><mi>w</mi></msub>
	</mfenced></math>
	are computed as follows:</p><div class="informalequation"><math overflow="scroll">
	    <mtable><mtr><mtd>
		<msub><mi>x</mi><mi>w</mi></msub>
		<mgroupalign></mgroupalign>
		<mo>=</mo>
		<mgroupalign></mgroupalign>
		<mo>(</mo>
		    <msub><mi>x</mi><mi>nd</mi></msub>
		    <mo>+</mo>
		    <mn>1</mn>
		<mo>)</mo>
		<mfrac>
		    <mi>width</mi>
		    <mn>2</mn>
		</mfrac>
		<mo>+</mo>
		<mi>x</mi>
	    </mtd></mtr>
	    <mtr><mtd>
		<msub><mi>y</mi><mi>w</mi></msub>
		<mgroupalign></mgroupalign>
		<mo>=</mo>
		<mgroupalign></mgroupalign>
		<mo>(</mo>
		    <msub><mi>y</mi><mi>nd</mi></msub>
		    <mo>+</mo>
		    <mn>1</mn>
		<mo>)</mo>
		<mfrac>
		    <mi>height</mi>
		    <mn>2</mn>
		</mfrac>
		<mo>+</mo>
		<mi>y</mi>
	    </mtd></mtr></mtable>
	</math></div><p>Viewport width and height are silently clamped to a range
	that depends on the implementation. To query this range, call
	<a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>
	with argument <code class="constant">GL_MAX_VIEWPORT_DIMS</code>.</p></div><div class="refsect1" title="Errors"><a id="errors"></a><h2>Errors</h2><p><code class="constant">GL_INVALID_VALUE</code> is generated if either
	    <em class="parameter"><code>width</code></em> or
	    <em class="parameter"><code>height</code></em> is negative.</p></div><div class="refsect1" title="Associated Gets"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
	    <a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>
	    with argument <code class="constant">GL_MAX_VIEWPORT_DIMS</code>
	</p></div><div class="refsect1" title="See Also"><a id="seealso"></a><h2>See Also</h2><p>
	    <a class="citerefentry" href="glDepthRange"><span class="citerefentry"><span class="refentrytitle">glDepthRange</span></span></a>,
	    <a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>
	</p></div><div class="refsect1" title="Copyright"><a id="copyright"></a><h2>Copyright</h2><p>
	    Copyright © 2003-2004
	    Silicon Graphics, Inc. This document is licensed under the SGI
	    Free Software B License. For details, see
	    <a class="ulink" href="https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/" target="_top">https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div>
